faft: remove a redundant method from firmware_Cr50RMAOpen.

tpm_is_disabled() is redundant to cr50_test.tpm_is_responsive(),
which is introduced in crev.com/c/1316338.

CQ-DEPEND=CL:1316338
BUG=none
BRANCH=none
TEST=test_that --board=coral ${IP} firmware_Cr50RMAOpen
---------------------------------------------------------------------
.../results-1-firmware_Cr50RMAOpen                      [  PASSED  ]
.../results-1-firmware_Cr50RMAOpen/firmware_Cr50RMAOpen [  PASSED  ]
---------------------------------------------------------------------
Total PASS: 2/2 (100%)

Change-Id: I80dc7229fd7770b3beeb7ad000214c223ebc7189
Signed-off-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1474500
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Mary Ruthven <mruthven@chromium.org>
diff --git a/server/site_tests/firmware_Cr50RMAOpen/firmware_Cr50RMAOpen.py b/server/site_tests/firmware_Cr50RMAOpen/firmware_Cr50RMAOpen.py
index 8ed55d9..e22fa0e 100644
--- a/server/site_tests/firmware_Cr50RMAOpen/firmware_Cr50RMAOpen.py
+++ b/server/site_tests/firmware_Cr50RMAOpen/firmware_Cr50RMAOpen.py
@@ -86,11 +86,6 @@
         self.is_prod_mp = self.get_prod_mp_status()
 
 
-    def tpm_is_enabled(self):
-        """TPM is disabled if the tpm version cant be retrieved"""
-        return not self.host.run('tpm_version', ignore_status=True).exit_status
-
-
     def get_prod_mp_status(self):
         """Returns True if Cr50 is running a prod signed mp flagged image"""
         # Determine if the running image is using premp flags
@@ -265,7 +260,7 @@
 
         self.host.reboot()
 
-        if not self.tpm_is_enabled():
+        if not self.tpm_is_responsive():
             raise error.TestFail('TPM was not reenabled after reboot')
 
         # Run RMA disable to reset the capabilities.
@@ -279,7 +274,7 @@
         # The open process takes some time to complete. Wait for it.
         time.sleep(self.CHALLENGE_INTERVAL)
 
-        if self.tpm_is_enabled():
+        if self.tpm_is_responsive():
             raise error.TestFail('TPM was not disabled after RMA open')
 
         if self.cr50.get_wp_state() != self.WP_PERMANENTLY_DISABLED:
@@ -294,7 +289,7 @@
         # The open process takes some time to complete. Wait for it.
         time.sleep(self.CHALLENGE_INTERVAL)
 
-        if not self.tpm_is_enabled():
+        if not self.tpm_is_responsive():
             raise error.TestFail('TPM is disabled')
 
         # Confirm write protect has been reset to follow battery presence. The